Is it because smart people are more career oriented, and don't want to lose any chances on promotion/career climbing?
Being "set" before getting kids? i.e, financially stable, "oneitis" wife/gf, solid future plans.
I asked some of my old jr. high mates (that got knocked up/knocked up someone else pretty early) why they did it:
"Better to get the kids when you're young, so that you're "free" earlier when you get old"
"Didn't have any plans for life at that moment, besides, I receive child support"
Most of the people(around my age) that I know have kids, or even multiple kids, quit school after Jr. HS
A) Working like dogs at some dead-end job, paying child support
B) Receiving child support, not really doing anything
Could also just be that I'm from the white-trash, bum**** backwoods though